What are the 4 basic types of tissue?
- Nervous
- Epithelial
- Muscle
- Connective
What are the types of CT?
- Proper
Specialised
- Adipose
- Blood
- Bone
- Cartilage
- Haemopoietic (bone marrow and lymphoid)
What cells does CT arise from?
Mesenchymal stem cells
Suggest 6 functions of CT?
- Connects cells to form tissues, tissues to form organs and organs to form the body. Some CT provides support (cartilage/bone).
- Transport: medium for diffusion of nutrients and wastes.
- Protection: cushion between tissues and organs, and insulation (adipose).
- Storage (adipose).
- Defence against infection (blood/lymph/fixed and wandering cells)
- Wound healing (macrophages, fibroblasts, myofibroblasts).
What are the 3 general components of CT proper?
- Cells
- Fibres
- Ground substance
Which cells secrete the fibres (collagen) and ground substance of CT?
Fibroblasts
As well as producing CT, what is an important role of fibroblasts?
- Wound healing
- Scar tissue formation - myofibroblasts = modified fibroblasts containing actin. Responsible for wound contraction when tissue loss has occurred.
What are the 3 types of fibres in CT and why are these important?
- Collagen - flexible with high tensile strength
- Reticular - provide a supporting framework
- Elastin - allows tissue to recoil after stretch
What is the most common protein in our body?
- Collagen
- 1/4-1/3 of whole-body protein content
How many types of collagen do we have and which is the most common?
- 28
- Type I (90% of all collagen)
What is the difference between type I, II, III & IV collagen?
- Type I: fibrils (composed of alpha chain triple helix) aggregate into fibres and fibre bundles (e.g. tendons, organ capsules and skin dermis).
- Type II: fibrils do not form fibres (e.g. hyaline and elastic cartilage).
- Type III: fibrils form fibrils around muscle and nerve cells and within lymphatic tissues and organs - reticulin.
- Type IV: unique form present in basal lamina of basement membranes.
What are reticular fibres and where are they primarily found?
- Consist of type III collagen.
- Form an irregular anastomosing network throughout lymph nodes, with lymphocytes densely packed in the spaces between the fibres.
What are elastic fibres composed of?
- Primary component = elastin.
- Enfolds and is surrounded by fibrillin microfibrils.
Where are elastin fibres found?
- Occur in most CT but to widely varying degrees.
- Important role in:
~ dermis
~ artery walls (allows stretch and recoil)
~ lungs
~ elastic cartilage
Which disease is associated with abnormal elastic fibres?
- Marfan’s syndrome
- Autosomal dominant - abnormal expression of fibrillin gene
- Abnormally tall, arachnodactyly, frequent joint dislocation, risk of aortic rupture.
What is the ground substance of CT made up of?
- Proteoglycans = large macromolecules consisting of a core protein to which glycosaminoglycans (GAGs) are bound.
- High water content - viscous.
Why does ground substance have a high water content?
GAGs attract water as they are:
- strongly hydrophilic
- highly negatively charged - attract cations (e.g. sodium ions), causing water to be sucked into the matrix
Describe the properties of a unique GAG.
- Hyaluronic acid
- Bound to proteoglycans by a linker protein - forms giant hydrophilic macromolecules.
- Present in ground surface of cartilage - allows it to resist compression without inhibiting flexibility.